JPS6121493A - Cooling system piping structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to the construction of cooling system piping, and relates to a fast breeder reactor (FBR).
Large-scale sodium leak from sodium cooling system piping)
- In the event of a leak, sodium leaks from the concrete forming the room housing the pipes! '-Relates to a cooling system piping structure that prevents damage due to direct contact with walls.

[Technical background of the invention and its problems] Helium, a metal commonly used as a coolant for fast breeder reactors, is a chemically very active substance that reacts violently with oxygen and moisture. Therefore, in the event of a large-scale helium leak, it will react with a large amount of oxygen and hydrogen in the psalium atmosphere, releasing a large amount of heat. Furthermore, when leaked sodium comes into direct contact with the concrete walls forming a room housing pipes and equipment, -C hydrogen is generated due to the sodium-concrete reaction. Furthermore, the reaction heat heats the concrete and generates moisture in the concrete, which reacts with sodium, which also generates hydrogen. In this case, there is a risk that the structural strength of the concrete will deteriorate due to hydrogen accumulation and dehydration.

This will be explained in more detail using the case of the prototype reactor "Monjiyu" of the fast breeder reactor (hereinafter referred to as FBR) shown in FIGS. 8 to 10 as an example. As shown in FIG. 8, the power generation system consists of an outer circumference=1 concrete wall 21
The reactor vessel 23 housed in the reactor containment vessel 22 surrounded by The superheater 27, superheated steam 28, turbine 29, power generation 13
0. Power is generated by operating a power generation cycle consisting of a condenser 31, a circulation pump 32, a water supply pump 33, an evaporator 34, a secondary main circulation pump 35, and an air cooler 36.

However, since the primary sodium 24, which directly transfers the heat of the reactor core, is activated, measures against its leakage are particularly strict.
Not only the reactor vessel 23 but also the reactor containment vessel 22, which is the primary system atmosphere where the piping and equipment containing the primary sodium 24 are installed, is filled with nitrogen that is not reactive with sodium cum. The tank is filled with sodium to prevent sodium fires. Furthermore, in order to prevent sodium-concrete reactions, steel liners are placed over the entire surface of each site where piping and equipment are installed. On the other hand, in the case of secondary sodium 26, it is not radioactive, so the situation is not severe for primary sodium 24, but the reactor auxiliary building where most of the piping and equipment for secondary sodium 26 is installed. Since there is an air atmosphere inside the reactor 25, sodium fires are likely to occur, and prevention of such fires is extremely important for plant safety. This secondary sodium 26
In this case, for example, in a room where piping and equipment such as a superheater 27, an evaporator 34, a secondary main circulation pump 35, and an air cooler 36 are installed, a floor liner 37 is installed as shown in FIG.
Sodium leaked from each room is drained from the floor liner 37 to the lower layer through the communication pipe 38 and stored in the storage tank 39, or is stored in the fire suppression plate 40 ("
Drain into the storage liner 41 for suffocation and digestion,
It is accommodated in the A-bar flow tank 44. Also, the first
As shown in Figure 0, clamp parts 1 are arranged at appropriate intervals.
The sodium cooling system arrangement @ 11 surrounded and supported by 2 has an annulus space 13 and is kept warm by an insulation i+A 14 whose inside and outside are covered with an interior plate 15 and an exterior plate 16. However, if the input amount of sodium leaks from the pipe 11, the leaked sodium 1 to 18 will be transferred to the annulus space 13.
The heat insulating material 14 is further filled from the inner panel 15 and flows downward in the tube axis direction. When the flow of this leaked sodium 18 reaches the clamp part 12, the leaked sodium 18 concentrates in the part where the clamp part 12 cuts off the annulus space 13 because the clamp part 12 divides the annulus space 13 in the tube axis direction. Accumulation, heat insulating material 14, exterior plate 16
It breaks through and erupts into the surrounding area. This leaked sodium 18
In order to prevent a sodium-concrete reaction that would occur due to direct contact between the 18 and the concrete walls 42 forming the room, steel liners 43 are placed over all areas where the sodium 18 comes into contact. It's stretched out.

The above-mentioned sodium leakage measures prevent sodium fires, suppress sodium-concrete reactions, and ensure the strength of building concrete through IC, making a major contribution to plant safety. however,
According to this conventional method, all the walls, floors, and ceilings of the room that could come into contact with leaked sodium must be lined with liners, which is costly.
Therefore, in order to reduce costs, there has been an important demand for other prevention technologies to replace the liner.

In the nuclear power plant building, the sodium-lium cooling system piping 11 is formed of a horizontal piping section, a vertical piping section, and a reporting section. If a large leak of sodium occurs from the horizontal piping section, the leaked hlium will be spouted onto the floor liner 43 from the preheating heater outlet, which is not clearly shown in the diagram, and will be stored in the storage tank 39 through the communication pipe 38. Ru. If a large leak of sodium occurs from a vertical piping section, the leaked sodium will be
Preheating heater extraction 1] and the clamp part 12 that partitions the annulus space 13 spray out toward the wall of the room housing the pipes, damaging the wall.

Currently, economical considerations require that the wall liner be wiped off. Also, from the perspective of repair costs after an accident, it is necessary to reduce the number of damaged areas caused by leaked sodium. For this reason, it is desired to guide the leaked sodium generated from the vertical piping part to a part of the floor liner without polluting the walls of the storage room. [Object of the Invention] The present invention was created in view of the above-mentioned circumstances, and is intended to prevent leakage of aluminum from accumulating at the clamp part and spouting out of the heat insulating material, thereby damaging walls, etc. It is an object of the present invention to provide a cooling system piping structure that has the same movement as a liner in terms of safety and can achieve a significant cost reduction compared to the case where a liner is used.

[Summary of the Invention] In order to achieve the above-mentioned object, the present invention provides an envelope tube that covers a sodium cooling system piping with a necessary annulus space provided on its outer periphery, and a jacket tube that covers the sodium cooling system piping with a required annulus space provided around the outer periphery, and a jacket tube that covers the sodium cooling system piping with a required annulus space provided on the outer periphery, and The clamp part supports the cooling system piping so as to be partitioned in the direction, and the clamp is provided with a communication hole that communicates the adjacent annulus spaces with each other, and a valve is attached to the communication hole.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 7.

In FIG. 1, reference numeral 11 indicates a sodium cooling pipe, and this pipe 11 is formed into a predetermined pipe path by a plurality of clamp parts 12 that surround the pipe 11 and support it at predetermined intervals. The outer periphery of the pipe 11 is surrounded by a heat insulating material 4 with annulus spaces 13 spaced at regular intervals to keep the pipe 11 warm. The inside of the heat insulation 11J1/I is a metal interior board 1
5, the outside is similarly covered with a metal exterior plate 16 to protect the moisturizing moon 14.

The annulus space 13 is connected to the pipe 1 by the clamp part 2.
The clamp portion 12 is provided with a communication hole 7 that communicates between adjacent annulus spaces 13, and a gate valve 45 is attached to the communication hole 17.

In FIG. 2, reference numeral 45 is a gate valve, and this valve 45 functions to partition adjacent annulus spaces connected by the flow hole 17 except in the case of a major sodium leakage accident. The valve 45 is a thin metal plate made of aluminum, for example, and a portion thereof is attached to the clamp portion by screws or spot welding. By the way, from the standpoint of detecting minute leaks, it is necessary to keep the flow hole 17 closed except in the event of a major leakage accident. Therefore, the valve 45 is designed to block the flow of gas in the adjacent annulus space 13 that is connected to the flow hole 17, and to avoid affecting the detection performance of the sodium microleak detection using the gas sampling method. There is. However, if a sodium leakage accident occurs, the valve 45 will easily open due to the pressure of the sodium flowing through the annulus space 13.

If sodium leaks from the pipe 11, even if the sodium flows into the clamp part 12, it will flow downward through the flow hole 7 without being stagnant and will be stored in the overflow tank 44 or the like.

FIG. 3 shows a seven-lunge interior plate 48 included in the clamp part 12, or a communication hole 17 in the interior plate 5 that allows the flow of adjacent annulus spaces 13 to guide sodium leaking from the vertical piping section downward. An example is shown below. In general, a major leakage accident is assumed to be an accident in which a hole of DT (D: pipe diameter, T: pipe thickness) occurs in a pipe. For this reason, it is considered appropriate that the cross-sectional area of the flow hole 17 be shifted to the equivalent of DT. The flow holes 17 are communicated with each other by a flow pipe 46 passing through a gap 49 in the clamp portion 12 which has an interlocking structure as shown in FIG. The flow pipe 46 is connected to the flow hole 17
The interior plate 151 provided with this is attached by welding to the interior plate flange portion 48 that constitutes and covers a part of the clamp portion 2.

On the other hand, from the sodium microleakage detection system side, the annulus space 13 is provided in the clamp part 12 and communicated with it by a flow pipe 46. [Piping 1 as shown in Figure 5]
If the length of the sampling pipe 50 is considerably long, it is preferable to provide a sampling pipe 50 for each annulus space of about 10 m, and to sample the gas in each space partitioned by the pipe 50. By the way, problems arise in the performance of the micro leak detection side, such as the provision of the large leak communication hole 17, which makes it impossible to ensure the flow velocity distribution in the annulus space necessary for IC expansion and micro leak detection. For this reason, it is necessary to normally close the large leakage hole 17.

Therefore, a valve 45 is attached to the lower side of the sea urchin flow hole 7 described above, and a thin metal plate is used as the valve 45. The valve 45 is attached to the interior plate 1 as shown in FIGS. 6 and 7.
5 or the interior plate flange portion 48 by spot welding, or by screwing one side of the valve 45. In a large sodium leakage accident, for example in the case of Monjiyu, the leaked sodium was DT (~13Cm).
It blows out from the hole with a pressure of about 5 kg/cm2. From now on, a force equivalent to DT (~65!J) will be applied to the valve 45. This force causes the valve 45 to open. The valve 45 that was opened at the time of the accident is replaced with a new one during repair after the accident. The valve 45 normally closes the flow hole 17 and fully functions to open only in the event of an accident.

[Effects of the Invention] According to the present invention, the leaked sodium does not concentrate on the clamp portion 12 and break through the heat insulating material 14 and the exterior plate 16, and spout out to the surroundings, as in the conventional case. There is no need to put a liner on the concrete wall to protect it from water.

By providing a circulation hole 7 that connects the adjacent annulus spaces 3 to each other in the clamp part 2 that partitions the annulus space 13 in the direction of the sodium cooling system piping 11, the pipe 1 can be accommodated. There is no need to line the concrete walls and ceilings that make up the room, and it is only necessary to line the low parts of the floors and walls. Therefore, the wall and ceiling liners conventionally used can be omitted, resulting in a significant cost reduction. Furthermore, in the event of a large-scale sodium leak from the pipe 11, the range of damage caused by the leaked sodium can be kept small, and the cost of maintenance after the accident can be significantly reduced.

[Brief explanation of drawings]

FIGS. 1 to 7 are for explaining one embodiment of the present invention. FIG. 1 is a partial sectional view showing the valve in an open state, and FIG. 2 is a partial cross-sectional view showing the valve in a closed state. 3 and 4 are perspective views of FIG. 1, FIG. 5 is an enlarged sectional view of the connected state of FIG. 4, and FIG. 6 is an enlarged view of the main parts of FIG. 2. 7 is a perspective view partially showing the main part of FIG. 6, FIG. 8 is a schematic diagram to explain the outline of the fast breeder reactor, and FIG. 9 is a diagram showing measures against leakage of secondary sodium. FIG. 10, which is a cutaway perspective view for explanation, is a sectional view of a conventional sodium cooling system piping. DESCRIPTION OF SYMBOLS 11...1 helium cooling system piping, 12...clamp part, 13...annulus space, 14...thermal insulation material, 15...interior board, 16
...Exterior plate, 17...Flow hole 18...Leaked sodium, 21...Peripheral concrete wall, 22...Reactor containment vessel, 23...Reactor vessel, 2
4...Primary sodium, 25...Reactor auxiliary building,
26...Secondary sodium, 27...Superheater, 28.
...superheated steam, 2...turbines, 30...
Generator, 31... Condenser, 32... Circulation pump, 33... Water supply pump, 34... Evaporator, 35... Secondary main circulation pump, 36... Air cooler, 37...floor liner, 38
...Communication pipe, 39...Storage tank, 40.
...Fire suppression board, 41...Storage liner, 42...
・Concrete wall, 43...) A, 44...A-
Bar 70-tank, 45...valve. Application attorney Chikara Kikuchi Department 19
, 4'], ,,, G
. Figure 1 Figure 2 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] (1) A cooling system piping for sodium, an envelope tube that covers the cooling system piping by providing a required annulus space around the outer periphery of the cooling system piping, and an envelope tube that covers the cooling system piping with the required annulus space formed on the outer periphery of the cooling system piping. A clamp part that supports the cooling system piping in a partitioned manner, a circulation hole provided in the clamp part that communicates with each other adjacent annulus spaces, and a valve attached to the circulation hole. cooling system piping structure.